Strain Field and Damage Evolution of Granite under Three-Point Bending Test

The granite three-point bending test was carried out, statistics, entropy and energy theories were introduced, and variance, entropy and deformation energy density were proposed as quantitative characterization indexes of strain field to quantitatively study the evolution law of strain field during rock failure process. On this basis, from the perspective of surface damage of strain field, the damage evolution law of rock deformation and failure process under three-point bending condition was studied with the help of quantitative characterization indexes of strain field. The results show that the three indexes of strain field variance, entropy and deformation energy density can quantitatively describe the evolution of strain field in granite fracture process under three-point bending. Based on the strain field surface damage analysis, it is found that the proportion of damage after the peak load is about 90% under the three-point bending test of granite, showing the characteristics of rapid development of post-peak damage. In contrast, the two indexes of strain field variance and deformation energy density can describe the damage evolution characteristics of granite under three-point bending test, and the rapid decline of entropy can be used as the precursor characteristics of granite fracture.